Biology. any natural or artificial process that results in differential reproduction among the members of a population so that the inheritable traits of only certain individuals are passed on, or are passed on in greater proportion, to succeeding generations.Compare natural selection, sexual selection, kin selection, artificial selection.

Linguistics.

the choice of one form instead of another in a position where either can occur, as of ask instead of tell or with in the phrase ask me.

the choice of one semantic or syntactic class of words in a construction, to the exclusion of others that do not occur there, as the choice of an animate object for the verb surprise.